Lighting state detection for a vehicle trailer

ABSTRACT

A towing vehicle includes a towing control unit with circuitry to detect whether a light is connected to the electrical harness electrically coupling the vehicle to the trailer. The towing control unit may include lamp connectivity circuits for, for example, the left turn signal and the right turn signal. To determine whether the turn light is connected, the corresponding connectivity circuit periodically generates a test signal. Based on characteristics of a response signal to the test signal. The connectivity circuit determines whether the corresponding turn signal light of the trailer is connected based on a response to the test signal. The connectivity circuit may distinguished whether an incandescent-based turn signal light, a light emitting diode (LED)-based turn signal light, and an open circuit is sensed based on the characteristics of the response signal.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 63/129,924, entitled “LIGHTING STATE DETECTION FOR A VEHICLETRAILER,” filed Dec. 23, 2020, the entirety of which is herebyincorporated by reference.

TECHNICAL FIELD

The present invention is generally related to vehicles with a towingcapacity and, more specifically, a towing/lighting controller for avehicle, such as a towed vehicle.

BACKGROUND

Modern trailers are both mechanically coupled (e.g., via a hitch, etc.)and electrically coupled (e.g., via a wire harness, etc.) to a towingvehicle. The trailer often includes lights, such as tail lights, turnsignals, reverse lights, running lights, stoplights, fog lights, parklights, auxiliary lights, etc., that correspond to lights on the towingvehicle. The electrical connection is configured so the trailer lightsmimic the vehicle lights in operation. In particular, to promote safety,the turning lights of the trailer must signal the turning intentions ofthe driver in the same manner the vehicle turning lights do. Similarly,the brake lights of the trailer must signal the braking of the towingvehicle. Because the trailer lights are not visible from the cab of thevehicle, checking whether the turning and/or braking lights are properlyconnected to the vehicle requires getting out of the cab or having asecond person who can check the lights as they manipulated by the firstperson. Also, while driving, it is important to know the status of ofthe lights on a trailer/towed vehicle, i.e., if it is operational or notoperational, within a short time after the status changes.

SUMMARY

This disclosure relates to detection of a connection to lights of atrailer, such as turn signal lights. As described below, a towingvehicle may include a towing control unit that includes circuitry todetect whether a light is connected to the electrical harnesselectrically coupling the vehicle to the trailer. In some examples, thetowing control unit may include a lamp connectivity circuit for the leftturn signal and a connectivity circuit for a right turn signal as wellas the brake signal and other lights like running, fog, reverse,auxiliary, park etc. To determine whether the turn light and/or brakelights (or any of the other lights) is connected, the correspondingconnectivity circuit periodically (e.g., every 20 millisecond (ms),every 100 ms, every 250 ms, etc.) generates a test signal. Based oncharacteristics of a response signal to the test signal, theconnectivity circuit (or, in some examples, processing circuitry coupledto the connectivity circuitry) determines whether the corresponding turnsignal light and/or braking light of the trailer is connected. In someexamples, the connectivity circuit may distinguish a state of the turnsignal light between an incandescent-based turn signal light, a lightemitting diode (LED)-based turn signal light, and an open circuit (i.e.no connected turn signal and/or brake light) based on thecharacteristics of the response signal. In some such examples, theconnectivity circuit may determine the state based on a timing betweenthe start of the test signal and rising edge of the response signal.

Moreover, the lights of the towed vehicle being electrically andoperatively coupled with the lights of the towing vehicle can beutilized to confirm that the towed vehicle is still operatively coupledwith the towing vehicle.

An example system to determine a connection state of lamps of a trailerincludes connectivity circuitry and processing circuitry. Theconnectivity circuitry is electrically coupled to a connector to providea test signal to the lamps of the trailer. The connectivity circuitryalso conditions a response signal indicative of the connection state andthe load profile. The processing circuitry is electronically coupled tothe connectivity circuitry. The processing circuitry determines theconnection state and the load profile of the lamps of the trailer basedon the response signal when the lamps of the trailer are off. In someexamples systems, the processing circuitry distinguishes between atleast three different load profiles. In some example systems, theprocessing circuitry distinguishes between (a) a first load profileindicative that no lamps of the trailer are connected to the connector,(b) a second load profile indicative that the lamps of the trailer areincandescent-based lamps, (c) and a third load profile indicative thatthe lamps of the trailer are light emitting diode-based lamps. In somesystems, the processing circuitry distinguishes between the first loadprofile, the second load profile, and the third load profile based ontiming characteristic of the response signal. In some example systems,the processing circuitry determines that load profile of the lamps ofthe trailer is the first load profile based on the timing characteristicbeing below a first threshold. In some example systems, the processingcircuitry determines that load profile of the lamps of the trailer isthe second load profile based on the timing characteristic being betweena first threshold and a second threshold greater than the firstthreshold. In some example systems, the processing circuitry determinesthat load profile of the lamps of the trailer is the third load profilebased on the timing characteristic being above a second threshold thatis greater than the first threshold. In some example systems, the lampsare turn signal lamps of the trailer. In some example systems, the lampsare at least one of running lamps, fog lamps, reverse lamps, auxiliarylamps, or park lamps.

In some examples, the system includes lamp control circuitry that isseparate from the connectivity circuitry. The lamp control circuitrycontrols the on/off state of the lamps of the trailer. Additionally, thelamp control circuitry is communicably coupled to an electronic controlunit of a towing vehicle. In some example systems, the processingcircuitry defines a state machine to asynchronously control theconnectivity circuitry to provide the test signal and determine theconnection state and load profile of the lamps of the trailer. In someexample systems, the connectivity circuitry includes a right lampconnectivity circuit and a left lamp connectivity circuit. Theprocessing circuitry defines a test cycle to periodically test theconnection state and the load profile of the lamps of the trailer bycausing the right lamp connectivity circuit to produce a first testsignal at a first time that generates a first response signal andcausing the left lamp connectivity circuit to produce a second testsignal at a second time that generates a second response signal. In someexample systems, the processing circuitry defines a duration of the testsignal(s) such that the lamps, when present, do not visibly illuminatein response to the test signal. In some example systems, the processingcircuitry detects when the lamps are powered on. The processingcircuitry suspends generating the test signal while the lamps arepowered on in response to detecting that the lamps are powered on.

In some example systems, the test signal is a first test signal. In suchexample systems, the connectivity circuitry provides a second testssignal to the same one of the lamps as the first test signal. In somesuch example systems, the processing circuitry measures a first voltageat first current threshold of a signal generated in response to thefirst test signal and a second voltage at a second current threshold ofa signal generated in response to the first test signal. The firstcurrent threshold is set to be different than the second currentthreshold. In some such example systems, the processing circuitrydetects a presence of corrosion between the connector and the lampsbased on a different between the first voltage and the second voltage.

An example system to determine a connection state and a load profile oflamps of a vehicle includes connectivity circuitry and processingcircuitry. The connectivity circuitry is directly electrically coupledto the lamps to provide a test signal. The connectivity circuitry alsoconditions a response signal indicative of the connection state and theload profile. The processing circuitry is electronically coupled to theconnectivity circuitry. The processing circuitry determines theconnection state and the load profile of the lamps of the trailer basedon the response signal when the lamps of the trailer are off.

An example method of determining a connection state of lamps of atrailer includes monitoring an on/off state of the lamps of the trailer.The example method also includes, when the lamps of the trailer are off,(a) generating a first ramp signal for a first one of the lamps. (b)monitoring a first response signal generated in response to the firstramp signal, (c) generating a second ramp signal for a second one of thelamps, (d) monitoring a second response signal generated in response tothe second ramp signal, and (e) categorizing the connection state and aload profile of the lamps of the trailer based on the first and secondresponse signals. In some example methods, categorizing the connectionstate of the lamps of the trailer based on the first and second responsesignals includes distinguishing between at least three load profiles. Insome example methods, categorizing the load profile of the lamps of thetrailer based on the first and second response signals includesdistinguishing between (a) a first load profile indicative that no lampsof the trailer are connected to the connector; (b) a second load profileindicative that the lamps of the trailer are incandescent-based lamps;and (c) a third load profile indicative that the lamps of the trailerare light emitting diode-based lamps.

In some example methods, distinguishing between the first load profile,the second load profile, and the third load profile includesdistinguishing between the first load profile, the second load profile,and the third load profile based on a timing characteristic of theresponse signals. In some example methods, distinguishing between thefirst load profile, the second load profile, and the third load profileincludes determining that the load profile of each of the lamps of thetrailer is the first load profile based on the timing characteristicsbeing below a first threshold. In some example methods, distinguishingbetween the first load profile, the second load profile, and the thirdload profile includes determining that the load profile of each of thelamps of the trailer is the second load profile based on the timingcharacteristic being between a first threshold and a second thresholdgreater than the first threshold. In some example methods,distinguishing between the first load profile, the second load profile,and the third load profile includes determining that the load profile ofeach of the lamps of the trailer is the third load profile based on thetiming characteristic being above a second threshold that is greaterthan the first threshold.

An example method of determining a connection state of a lamp of atrailer includes monitoring an on/off state of the lamp of the trailer.The example method also includes, when the lamp of the trailer is off,(a) generating a ramp signal for the lamp, (b) monitoring a responsesignal generated in response to the ramp signal, and (c) categorizingthe connection state and a load profile of the lamps of the trailerbased on the response signal.

An example trailer light controller includes a left lamp connectivitycircuit, a right lamp connectivity circuit, a left lamp control circuit,a right lamp control circuit, and processing circuitry. The left lampconnectivity circuit is electrically coupled to a connector to connectto a left lamp of a trailer. The left lamp connectivity circuit producesa first test signal and conditions a first response signal. The firstresponse signal has a first timing characteristic based on a connectionstatus and a load profile of the left lamp. The right lamp connectivitycircuit is electrically coupled to the connector to connect to a rightlamp of a trailer. The right lamp connectivity circuit to produces asecond test signal and conditions a second response signal. The secondresponse signal has a second timing characteristic based on a connectionstatus and a load profile of the right lamp. The left lamp controlcircuit coupled to the connector to connect to the left lamp to controlthe on/off state of the left lamp. The right lamp control circuitcoupled to the connector to connect to right lamp to control the on/offstate of the right lamp. The processing circuitry (a) categorizes theconnection state and the load profile of the left lamp based on thefirst timing characteristic of the first response signal, and (b)categorizes the connection state and the load profile of the right lampbased on the second timing characteristic of the second response signal.In some example trailer light controllers, for each of the left andright lamps, the processing circuitry distinguishes between a first loadprofile indicative that the corresponding lamp is not connected to theconnector, and a second load profile indicative that the correspondinglamp is one of an incandescent-based lamp or a light emittingdiode-based lamp.

BRIEF DESCRIPTION OF THE DRAWINGS

Operation of the present disclosure may be better understood byreference to the following detailed description taken in connection withthe following illustrations, wherein:

FIG. 1 is a conceptual diagram for a system to determine a connectionstate of lights of a trailer operating in accordance with the teachingsof this disclosure. In the illustrated examples, turn signal aredepicted as an example. However, the system may be used for other typeslamps/lights.

FIG. 2 illustrates example circuits to generate test signals andresponse signals to determine the connection state of lights of atrailer operating with lights in the off state in accordance with theteachings of this disclosure.

FIG. 3 illustrates a conceptual diagram of a test signal and exampleresponse signals to determine the connection state of lights of atrailer in accordance with the teachings of this disclosure.

FIGS. 4A, 4B, and 4C illustrate example measurements of an example testsignal and example response signals to determine a connection state oflights of a trailer in accordance with the teachings of this disclosure.

FIGS. 5, 6, 7, 8, 9, 10, 11, and 12 are flowcharts of an example methodto determine the connection state of lights of a trailer in accordancewith the teachings of this disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. It is to be understood that other embodiments maybe utilized and structural and functional changes may be made withoutdeparting from the respective scope of the present disclosure. Moreover,features of the various embodiments may be combined or altered withoutdeparting from the scope of the present disclosure. As such, thefollowing description is presented by way of illustration only andshould not limit in any way the various alternatives and modificationsthat may be made to the illustrated embodiments and still be within thespirit and scope of the present disclosure.

As used herein, the words “example” and “exemplary” mean an instance, orillustration. The words “example” or “exemplary” do not indicate a keyor preferred aspect or embodiment. The word “or” is intended to beinclusive rather an exclusive, unless context suggests otherwise. As anexample, the phrase “A employs B or C,” includes any inclusivepermutation (e.g., A employs B; A employs C; or A employs both B and C).As another matter, the articles “a” and “an” are generally intended tomean “one or more” unless context suggests otherwise.

The present system can detect low current lights (such as LED lights) aswell as incandescent lights, can do this over a very short period oftime, and does this frequently to determine connectivity. This alloccurs without inadvertently illuminating the lights because of the lowcurrent and short duration of the ramp signal. Further, the presentsystem may determine the type of load (sometimes referred to as a “loadprofile”), such as an incandescent load, an LED load, or no load. Theload profile is indicative of what type, if any, lamp is connected tothe trailer lamp controller.

FIG. 1 is a conceptual diagram for a system 100 to determine aconnection state of lights 102A and 102B (collectively referred to as“lights 102) of a trailer operating in accordance with the teachings ofthis disclosure. While lights 102A and 102B are shown in the illustratedexamples, the system may also be utilized to detect other lights on thetowed vehicle, e.g., braking lights, auxiliary lights, fog, park,reverse or the like. Additionally, while the examples illustrate thesystem being used to detect the connection state or status of lights ofa towed vehicle or trailer, the system may additionally or alternativelybe used to detect the connection state or status of lights on the towingvehicle. Accordingly, examples below that disclose the system connectedto lights on a towed vehicle also may apply to any of the lights on atowing vehicle.

In the illustrated example, a vehicle or trailer electrical harnessincludes a trailer control unit 104 comprising circuitry to determinethe connection status of the lights 102. While turn signals aregenerally described below, the circuitry of the trailer control unit 104may be used to determine connection status of other lights. In theillustrated example, the turn signal detection unit 104 iscommunicatively coupled to a light controller unit 106 of the vehicle.The light control unit 106 is an electronic control unit (ECU) of thevehicle that is configured to control the lights of the vehicle,including the turn signals of the vehicle. The light control unit 106controls the lamp control circuits (not shown) of the vehicle toactivate the turn signals of the vehicle (not shown).

In the illustrated example, the trailer control unit 104 includes leftturn lamp control circuitry 108A and right turn lamp control circuitry108B (collectively “turn lamp control circuits 108”) that operate thelights 102A and 102B, respectively. The turn lamp control circuits 108may, for example, receive a signal or signals from the light controlunit 106 to activate the lights 108 in parallel with the correspondinglights of the vehicle. This is when the lights are turned on at desiredillumination in ‘ON-state’. In the illustrated example, the trailercontrol unit 104 also include processing circuitry 110, left turn lampconnectivity circuitry 112A and right turn lamp connectivity circuitry112B (collectively “turn lamp connectivity circuits 112” or“connectivity circuits 112”). The turn lamp connectivity circuits 112determine off-state connectivity. Off-state connectivity is used todetermine if the lights (e.g., lights 102) are connected (or operativelyconnected) while the lights are off. In some examples, the turn lampconnectivity circuits 112 can detect the connectivity of the light 102without turning on the lights 102 and causing no visible illumination ofthe lights 102. This is challenging because a light emitting diode(LED)-based lights require a relatively small amount of current toilluminate. As described below, the turn lamp connectivity circuits 108may determine on-state connectivity to detect whether the lights 102 areconnected when the lights 102 are turned on. The connectivity in ONstate is determined by measuring the current flowing in the lights. Thetype of lamp can be determined based on the amount of the current. Forexample, the incandescent lamps carry more current than LED lamps. Thereshould be none or very little current when there is no load.

As described below, the processing circuitry 110 controls the turn lampconnectivity circuits 112 to provide a test signal to the lights 102 andto interpret the response signal to determine the connection state ofthe light 102. In the illustrated example, the processing circuitry 110is incorporated into the trailer control unit 104. Alternatively, insome examples, the processing circuitry 110 as described herein may beincorporated into another ECU, such as the light control unit 106 or anon-board computing platform, etc. Alternatively, in some examples, theprocessing circuitry 110 may be a separate ECU that is communicativelycoupled to the trailer control unit 104 and light control unit 106. Insome examples, the trailer control unit 104 may use this determinationas a proxy for whether or not the trailer is connected to the vehicle.The processing circuitry 110 may be any suitable processing device orset of processing devices such as, but not limited to: a microprocessor,a microcontroller-based platform, a suitable integrated circuit, one ormore field programmable gate arrays (FPGAs), and/or one or moreapplication-specific integrated circuits (ASICs) or discrete electronichardware.

As described below, the turn lamp connectivity circuits 112 generatetest signal and shape the response signal based on the connection stateof the lights 102. An example of the turn lamp connectivity circuits 112is illustrated in FIG. 2. For example, FIG. 2 illustrates an example ofthe left turn lamp connectivity circuitry 112A and an example of theright turn lamp connectivity circuitry 112B. The characteristics of theresponse signal change depending on whether an incandescent-based turnsignal light is connected to the wire harness, an LED-based turn signallight is connected to the wire harness, no turn signal light isconnected to the wire harness (e.g., an open circuit). In some examples,the turn lamp connectivity circuits 112 cause the response signal tohave different timings of a changing edge (e.g., a rising edge, etc.) ofthe response signal depending on the type, characteristics, andconnection state of the lights 102. The processing circuitry 110 maydetermine the connection state of the lights 102 by detecting whichthreshold timing interval in which the changing edge of the responsesignal rises. For example, the processing circuitry 110 may determinethe type, characteristics, and connection state of the lights 102 bydetecting which threshold timing interval between the falling edge andrising edge of the response signal.

FIG. 3 is a conceptual diagram of a ramp signal 300 that is presented toa light terminal and responses 302A, 302B, and 302C (collectively“responses 302”). As described below, the ramp signal 300 is generatedwhen a test signal 301 is a logical “ON” value. In the illustratedexample of FIG. 3, the reference voltage (e.g., 5 volts) is a logical“OFF” value and ground (e.g., 0 volts) is a logical “ON” value. However,voltages that represent logic the logical “ON” value and the logical“OFF” value may be defined in any manner. The ramp signal 300 may becaused by the test signal 301 transitioning from a reference voltage toground which turns on a transistor that supplies voltage to a capacitorthat generates the ramp signal 300. In some examples, ramp signal 300 isconverted to a linear ramp when the capacitor is a bootstrap capacitorthat is, for example, 1 μF. The linear ramp 300 starts as a firstvoltage level (e.g., zero volts) and ramps to a second voltage level304. In some examples, the second voltage level 304 is the batteryvoltage. Alternatively, in some examples, the second voltage level 304is generated by a voltage regulator at a voltage different than thebattery voltage (e.g., 9.5V, etc.). In the illustrated example, the rampsignal 300 ramps to the second voltage level 304 exponentially.Alternatively, in some examples, the ramp signal 300 ramps to the secondvoltage level 304 linearly. In the illustrated example, the processingcircuitry 110 defines threshold timing intervals 306A, 306B, and 306C(collectively “threshold timing intervals 306”). The threshold timingintervals 306 define a period of time that, if response 302 falls belowa threshold value within that threshold timing intervals 306, theprocessing circuitry 110 determine that light connection is in acorresponding state (e.g., whether the lamp is connected and, if so, thetype of the lamp, etc.). In the illustrated example, an incandescentthreshold timing interval 306A defines a period of that in which theleading edge is indicative of an incandescent light being connectedelectrically coupled to the trailer control unit 104 (e.g., via the wireharness, etc.). As one example, the incandescent threshold timinginterval 306A may be from 0 microseconds (μs) to 210 μs, the LEDthreshold timing interval 306B may be from 210 μs to 559 μs, and theopen circuit threshold timing interval 306C may be any interval greaterthan 559 μs. In such an example, the total length of the ramp signal 300may be 700 μs. The duration of the ramp signal 300 is configured suchthat lamps 102 do not visibly illuminate under the influence of the rampsignal 300. In the illustrated example, three threshold timing intervals306 are defined to distinguish between incandescent lights and LEDlights and open load. In some examples, fewer or more threshold timingintervals may be defined.

Lamp detection occurs periodically in OFF state of the lamp. In someexamples, the period is either 250 ms or 500 ms (sometimes referred toas the “repetition period”). The period is frequent to, for example,almost immediately detect a disconnection. In some examples, the rampsignal 300 may be generated twice in the repetition period, with a delay(e.g., 12 ms) between each ramp signal 300. For example, the ramp signal300 for the left turn lamp connectivity circuitry 112A may be the firsttest signal in the repetition period, and the ramp signal 300 for theright turn lamp connectivity circuitry 112B may be the second testsignal in the repetition period. In some examples, when more than twolights are to be tested, the ramp signal 300 may be generated a numberof times equal to the number of lights 102 to be tested in therepetition period.

Alternatively or additionally, in some examples, the trailer controlunit 104 or, more specifically, connectivity circuits 112, may beduplicated for each lamp/light for which connectivity is to be tested.For example, the trailer control unit 104 may include a connectivitycircuit 112 for each lamp/light of the towed vehicle. Alternatively, insome examples, the system 100 may include multiple trailer control units104 to test connectively of different sets of lamps/lights. In someexamples, the trailer control unit 104 may test connectivity of a set(e.g., two, three, four, etc.) of the lights/lamps of the towed vehicle,but not all of the lamps/lights of the towed vehicle. In some examples,the system may include multiple trailer control units 104. Additionally,in some such examples, when multiple trailer control units 104 testconnectivity of the lights/lamps of the towed vehicle, each of thetrailer control unit 104 may be directly (e.g., via a direct data bus,such as a serial data bus, etc.) or indirectly (e.g., via a vehicle databus, such as a Controller Area Network (CAN bus), etc.) communicativelycoupled to communicate with one another and/or with a single computingdevice (e.g., the light controller ECU 106), which may be on the towedor towing vehicle.

When a light is not connected, the output of the turn lamp connectivitycircuitry 112 (e.g., the response signal 302C) generally mimics theinput of turn lamp connectivity circuitry 112 (e.g., the test signal301) and current doesn't conduct through the open circuit. When a lightis connected current eventually conducts through the light (e.g.,relatively quickly for an incandescent lamp, relatively longer for anLED lamp). As described below, the circuitry of the turn lampconnectivity circuitry 112 may be configured to detect, directly orindirectly, when this lamp current exceeds a threshold value.

FIG. 2 illustrates examples of comparator circuits 200A and 200B withinthe turn lamp connectivity circuitry 112 configured to detect the changeof the current. In some examples, the input of the comparator circuits200A and 200B may be configured such that the voltage on the input isgreater than a reference voltage (e.g., in non-inverting input ofcomparator circuit 200A) when the current conducted by the light due tothe test signal 301 satisfies (e.g., is greater than or equal to) athreshold current (e.g., 500 uA, 700 uA, etc.). Accordingly, the outputof the comparator circuits 200A and 200B may (a) be at a high voltage(e.g., a supply voltage, etc.) when the current related to the responsesignal 302 is above the threshold current (e.g., 500 uA, 700 uA, etc.)and (b) be at a ground when the voltage of the response signal 302 isbelow the threshold current. In the illustrated example of FIG. 2, Zenerdiode 208 and resistors 210A and 210B determine the current.Alternatively or additionally, other circuitry, such as one using a hallsensor, may be used to directly or indirectly detect when the currentconducted though the light is above a current threshold. In someexamples, an edge detector within the processing circuitry 110 or ECU106 stops a timer begun at the start of the test signal 301 when thechanging edge (e.g., a rising edge) of the response signal output by thecomparator cause by the response 306 is detected. In some examples, thesensitivity of the turn lamp connectivity circuitry 112 may be changedby adjusting the threshold current. In some examples, incandescentlights can be detected because incandescent lights generally conductcurrent quicker compared to an LED light.

FIGS. 4A, 4B, and 4C illustrate examples of a test signal 400 thatcauses the ramp signal 300 of FIG. 3 and the response signals 402A,402B, and 402C (collectively “response signals 402”) based on theresponses 306A, 306B, and 306C of FIG. 3. In the illustrated example ofFIG. 2, input 204 receives the test signal 400, output 206A outputs theresponse signal 402 for the left turn lamp control circuitry 108A, andoutput 206B outputs the response signal 402 for the right turn lampcontrol circuitry 108B. FIG. 4A illustrates a test signal 400 andcorresponding response signal 402A when an incandescent light isconnected. In the illustrated example, the response signal 402A changesfrom a logical high voltage (e.g., 5 volts) to a logical low voltage(e.g., ground) when the corresponding response 306A is indicative thatthe light 102 being tested in conducting current above a threshold,which is, in some examples, a current threshold. Because FIG. 4Aillustrates a scenario when incandescent lights are used for the lights102, the response 302A is indicative of the light conducting currentabove the threshold current quickly resulting in a relatively shortresponse signal 402A (as measured from the falling edge 404 of the testsignal 400 to the rising edge 406 of the response signal 402A).Resistors 212A and 212B of FIG. 2 cause a delay between the falling edge404 of the test signal 400 and the corresponding falling edge of theresponse signal 402A, 402B and 402C. FIG. 4B illustrates the test signal400 and corresponding response signal 402B when an LED light isconnected. In the illustrated example, the response signal 402B changesfrom a reference voltage (e.g., 5 volts) to ground when thecorresponding response 302B is indicative that the light is conductingcurrent above the current threshold. Because FIG. 4B illustrates ascenario when LED lights are used for the lights 102, the response 302Bis indicative of the light conducting above the threshold current beforethe test signal 400 ends resulting in a relatively shorter responsesignal 402B (as measured from the falling edge 404 of the test signal400 to the rising edge 406 of the response signal 402B) compared to whenlights 102 are not connected. FIG. 4C illustrates the test signal 400and corresponding response signal 402C when no light is connected.Because FIG. 4C illustrates a scenario when lights 102 are notconnected, the response 302C is indicative of no current being conductedresulting in a response signal 402A (as measured from the falling edge404 of the test signal 400 to the rising edge 406 of the response signal402C) that is similar to the test signal 400.

The trailer control units 104 performs the connection tests frequently(e.g., once every, 250 ms, once every 500 ms, once every 1000 ms, etc.)to discover a disconnection status or confirm a connection status of thelamps/lights. The trailer control units 104 may to send a signal to aprocessor or other device, such as for example, a brake controller, adisplay on a towing vehicle, a smart phone or any other device that maybe communication with the trailer control units 104 to identify eitheror both of a connected or disconnected status for the lights/lamps ofthe towed vehicle. The trailer control units 104 may also detect whetherthe applicable lights/lamps are operational.

In some examples, the trailer control units 104 may define two differentcurrent thresholds to determine whether there is corrosion in thesystem. The trailer control units 104 may analyze the voltage todetermine whether there is potentially corrosion present. For example,the trailer control unit 104 may use 350 μA and 700 μA currentthresholds. The trailer control unit 104 first applies a currentthreshold of 350 μA and then detect the resultant voltage across thesystem. The trailer control unit 104 may then apply a current thresholdof 700 μA and measure the resultant voltage. When the voltage after thesecond current threshold (e.g., the 700 μA threshold) is approximatelytwice that of the voltage after the first current threshold (e.g., the350 μA threshold), the trailer control unit 104 determines that there iscorrosion in the system and provides a warning signal to the user toalert them of the corrosion present. When the voltage after the secondcurrent threshold is applied is not twice the voltage after the firstcurrent threshold (or some linear correlation thereto), the trailercontrol unit 104 determines that there is no corrosion present (e.g.,because the response of the LED would be non-linear). While specificexamples of a first current threshold and a second current threshold areprovided, the present disclosure isn't limited to these current levels.Any appropriate current level may be utilized without departing from thepresent teachings.

FIG. 5 is an example flowchart of a state machine 500 operated byprocessing circuitry 110 to determine the connection state of the lights102. The descriptions of FIGS. 5-12 use example names of flags andvariables to facilitate tracking of the status of the connectivitytests. Flags are Boolean variables that each signal a particularcondition or status that may be used, for example, to track the statusof the corresponding condition is a system (such as a state machine)that involves asynchronous processing. Such names are examples only. Theillustrated state machine 500 defines a first time loop (e.g., a 1 msloop) (502), a second time loop (e.g., a 2 ms loop) (504), a third timeloop (e.g., a 5 ms loop) (506), a fourth time loop (e.g., a 10 ms loop)(508), and fifth time loop (e.g., a 20 ms loop) (510). These loops 502,504, 506, 508, and 510 facilitate actions being taken at everycorresponding time interval. For example, the second time loop (504) maytrigger actions every two milliseconds and the fifth time loop (510) maytrigger actions every twenty milliseconds. Some actions are triggered bythe second time loop (504). In the illustrated example, connectivitytests are trigger by the second time loop (e.g., every 2 ms) (see FIG. 6below) (505). Some actions are triggered by the fourth time loop (508).In the illustrated example, a determination of the connection state ofthe lights is triggered by the fourth time loop (e.g., every 10 ms) (seeFIG. 12 below) (509). Some actions are triggered by the fifth time loop(510) (e.g., every 20 ms).

In the illustrated example, at the fifth time loop (510), the processingcircuitry 110 determines whether a periodic output request is “ON”(e.g., or “TRUE,” etc.) and the battery voltage is between a thresholdinterval (e.g., 10-16V, etc.) (512). If periodic output request is “ON”and the battery voltage is between the threshold interval, theprocessing circuitry 110 performs short to battery voltage (S2V) testson the right light and the left light to set a left turn S2V flag and/ora right turn S2V flag (514).

Additionally, the processing circuitry 110 determines whether the leftturn S2V flag is set (514). If the left turn S2V flag is set (YES at516), the processing circuitry 110 sets the left turn state connectivitystart flag (518). If the left turn S2V flag is not set (NO at 516), theprocessing circuitry 110 clears the left turn state connectivity startflag (520). The processing circuitry 110 then determines whether theright turn S2V flag is set (522). If the right turn S2V flag is set (YESat 522), the processing circuitry 110 sets the right turn stateconnectivity start flag (524). If the right turn S2V flag is not set (NOat 522), the processing circuitry 110 clears the right turn stateconnectivity start flag (526).

FIG. 6 illustrates an example flowchart for determining a connectionstate of the lights 102. Initially, the processing circuitry 110determines whether the left turn off state connectivity flag is set andthe left lamp output is off (602). If the left turn off stateconnectivity flag is set and the left lamp output is off (YES at 602),the processing circuitry 110 increments a left turn off state counter(604). The processing circuitry 110 determines whether the left turn offstate counter is greater than or equal to a threshold amount of time(606). For example, the threshold may be set so that at least 10 ms havepassed (i.e., the counter is greater than equal to five when the test isrun on the 2 ms loop). If the left turn off state counter is greaterthan or equal to the threshold amount of time, (YES at 606), theprocessing circuitry 110 resets the left state connectivity test (608).For example, the processing circuitry 110 may reset the left turn offstate connectivity flag and clear the left turn off state counter.

The processing circuitry 110 then determines whether the lamp is readyfor the left state connectivity test (610) For example, the processingcircuitry 110 determines (a) a FET status of the left turn lamp isfalse, (b) a stop lamp request is false, (c) an event based outputrequest is false, and (d) a turn lamp request equals zero (610). If allof those conditions are true (e.g., the lamp is ready for the left stateconnectivity test) (YES at 610), the processing circuitry 110 initiatesthe left turn connectivity test and sets a left turn off stateconnectivity in progress flag to true (612). The method continues withmore functions (see FIG. 7).

If the left turn off state connectivity test in progress flag is not set(NO at 602), the processing circuitry continues to determine theconnection state of the right light 102B (see FIG. 8) (614).

FIG. 7 illustrates an example flowchart for determining a connectionstate of the left light 102A. The processing circuitry 110 enables theramp output (e.g., provides test signal 400 to cause ramp signal 300,etc.) (702). The processing circuitry 110 sets a global leftconnectivity test in progress flag (704). The processing circuitry 110sets a timer interrupt (e.g., a timer interrupt for 700 μs) (706). Theprocessing circuitry 110 resets the left connectivity results availableflag (708). The processing circuitry 110 determines whether any timer inrunning (710). When a timer is not running (NO at 710), the processingcircuitry 110 (a) reloads a light connectivity timer with 700 μs, (b)resets one or more delay flags (e.g., a 300 μs delay flag, a 500 μsdelay flag, a 700 μs delay flag, etc.), and (c) enables a rising edgeinterrupt to detect the rising edge of the response signal (e.g., theresponse signal 402) (712).

FIG. 8 illustrates an example flowchart for determining a connectionstate of the right light 102B. The processing circuitry 110 determineswhether the right turn off state connectivity flag is set and the rightlamp output is off (802). If the right turn off state connectivity flagis set and the right lamp output is off (YES at 802), the processingcircuitry 110 increments a right turn off state counter (804). Theprocessing circuitry 110 determines whether the right turn off statecounter is greater than or equal to a threshold (806). For example, thethreshold may be set so that at least 10 ms have passed (i.e., thecounter is greater than equal to five when the test is run on the 2 msloop). If the right turn off state counter is greater than or equal tofive, (YES at 806), the processing circuitry 110 resets the right stateconnectivity test by resetting the right turn off state connectivityflag and clearing the right turn off state counter (808). The processingcircuitry 110 then determines whether the right lamp is ready for theconnectivity test (810). For example, the processing circuitry 110determines (a) a FET status of the right turn lamp is false, (b) a stoplamp request is false, (c) an event based output request is false, and(d) a turn lamp request equals zero (810). If the right lamp is readyfor the connectivity test (e.g., all of those conditions are true) (YESat 810), the processing circuitry 110 starts the right turn connectivitytest and sets a right turn off state connectivity in progress flag totrue (812). The method continues with to determine the connection stateof the right light 102B (see FIG. 9).

If the right turn off state connectivity flag is not set and/or theright lamp output is on (NO at 802), the method ends.

FIG. 9 illustrates an example flowchart for determining a connectionstate of the right light 102B. The processing circuitry 110 enables theramp output (e.g., provides test signal 400 to cause ramp signal 300,etc.) (902). The processing circuitry 110 sets a global rightconnectivity test in progress flag (904). The processing circuitry 110sets a timer interrupt (e.g., a timer interrupt for 700 μs) (906). Theprocessing circuitry 110 resets the right connectivity results availableflag (908). The processing circuitry 110 determines whether any timer inrunning (910). When a timer is not running (NO at 910), the processingcircuitry 110 (a) reloads a light connectivity timer with 700 μs, (b)resets one or more delay flags (e.g., a 300 μs delay flag, a 500 μsdelay flag, a 700 μs delay flag, etc.), and (c) enables a rising edgeinterrupt to detect the rising edge of the response signal (e.g., theresponse signal 402) (912).

FIG. 10 illustrates an example flowchart for determining a connectionstate of the lights 102 by processing a rising edge interrupt. Theprocess may be triggered when the rising edge of the response signal 402is detected. The processing circuitry 110 sets the left or rightinterrupt flag depending on what test signal caused the interrupt(1002). The processing circuitry 110 determines whether the leftinterrupt flag is set and the global left connectivity in progress flagis set (1004). When both of these left related flags are set (YES at1004), the processing circuitry 110 (a) resets the global leftconnectivity in progress flag, (b) saves the current timer countervalue, (c) stops the current timer counter, (d) saves the timer periodvalue, (e) determines a difference between the value of the currenttimer counter and the timer period value, (f) sets the left connectivityresults available flag, and (g) resets the interrupt (1006).

When at least one of the left related flags is not set (NO at 1004), theprocessing circuitry 110 determines whether the right interrupt flag isset and the global right connectivity in progress flag is set (1008).When both of these right related flags are set (YES at 1008), theprocessing circuitry 110 (a) resets the global right connectivity inprogress flag, (b) saves the current timer counter value, (c) stops thecurrent timer counter, (d) saves the timer period value, (e) determinesa difference between the value of the current timer counter and thetimer period value, (f) sets the right connectivity results availableflag, and (g) resets the interrupt (1010). The processing circuitry 110resets the edge interrupt of the ports (1012).

FIG. 11 illustrates an example flowchart for determining a connectionstate of the lights 102 by processing a timer interrupt. This processtriggers when the off state timer interrupt is triggered to end the testsignal 400 (and thus end the ramp signal 300). For example, the offstate timer interrupt may be triggered 700 μs after the timer has begun.Initially, the processing circuitry 110 clears the off state timerinterrupt (1100). The processing circuitry 110 determines whether theglobal left connectivity timer flag is set (1102). When the global leftconnectivity timer flag is set (YES at 1102), the processing circuitry110 (a) clears the global left connectivity timer flag and (b) disabledthe ramp output (e.g., changes the test signal 400 from a ground voltageto a reference voltage) (1104).

When the global right connectivity timer flag is set (NO at 1102), theprocessing circuitry 110 determines whether the global rightconnectivity timer flag is set (1106). When the global rightconnectivity timer flag is set (YES at 1106), the processing circuitry110 (a) clears the global right connectivity timer flag and (b) disabledthe ramp output (e.g., changes the test signal 400 from a ground voltageto a reference voltage) (1108).

FIG. 12 illustrates an example flowchart for determining a connectionstate of the lights 102. The process may be executed every 10milliseconds (e.g., by the fourth time loop (508) of FIG. 5 above).Initially, the processing circuitry 110 determines whether the S2G orthe S2V flags are set (1202). When either flag is set (YES at 1202), theprocessing circuitry 110 sets a fault state and sets the lights toinactive (1204). When neither flag is set (NO at 1202), processingcircuitry 110 processes the available results (e.g., the resultsgenerated at steps 1004 or 1010 of FIG. 10 above) (1206). The processingcircuitry 110 determines whether either of the results available flagsare set (e.g., the left results available flag or the right resultsavailable flag) (1208). Then either of the results available flags areset (YES at 1208), the processing circuitry compares the results (e.g.,the difference between the value of the current timer counter and thetimer period value) to the first interval thresholds (e.g., between 210us and 560 μs) (1210). When the results fall within the first intervalthresholds (YES at 1210), the processing circuitry 110 (a) sets the lampin a debouncing state and (b) checks debouncing for 2 seconds (1212).The processing circuitry 110 determines whether debouncing wassuccessful (1214). When debouncing is successful (YES at 1214), theprocessing circuitry 110 sets the connection state of the correspondinglight 102 to be an LED light (1216).

When the results do not fall within the first interval thresholds (NO at1210), the processing circuitry 110 determines whether the results aregreater than a second threshold (e.g., greater than 560 μs, etc.)(1218). When the results are greater than the second threshold (YES at1218), the processing circuitry 110 (a) sets the lamp in a debouncingstate and (b) checks debouncing for 2 seconds (1220). The processingcircuitry 110 determines whether debouncing was successful (1222). Whendebouncing is successful (YES at 1222), the processing circuitry 110sets the connection state of the corresponding light 102 to beindicative no light (e.g., an open circuit) (1224).

When the results are not greater than the second threshold (NO at 1218),the processing circuitry 110 sets the connection state of thecorresponding light 102 to be an incandescent light (1226).

In some examples, the turn lamp connectivity circuitry 112 mayadditionally or alternatively include circuitry to perform an “on-state”connectivity test. Off-state connectivity tests are performed when thelights are off and on-state connectivity tests are performed when thelights are on. In some examples, an on-state connectivity test may beperformed after an off-state connectivity test. In some such examples,the results of each connectivity test may be stored and compared todetermine the connection state of the trailer. In detecting anincandescent light during an on-state connectivity test, the lightbehaves like a short circuit (e.g., a short circuit is indicative of anincandescent light because actual short circuits are very uncommon). Ifthe lamp connectivity circuitry 112 detects a change from a shortcircuit to an open circuit during the on-state connectivity test, theprocessing circuitry 110 sets the connection state of the correspondinglight 102 to be an incandescent light. To detect incandescent lights, anon-state connectivity test may be performed shortly after an off-stateconnectivity test as described above.

For the on-state connectivity test, to detect an LED light, the lampconnectivity circuitry 112 includes a smart FET that senses current. Thelamp connectivity circuitry 112 uses a calibrated K-factor for the LEDlights. To calibrate the K-factor, threshold current is used (e.g., 60mA, etc.). To determine the K-factor and calibrate the on-stateconnectivity test for detecting LED lights, a known load (e.g., 60 mA)is sent and then the output at the current sense end of the smart FET ismeasure. To calculate K-factor, the load current is divided by thecurrent at the current sense pin. This value is stored as a thresholdwith an actual measurement at the FET. The lamp connectivity circuitry112 determines that an LED light is connected when the current sensed bythe smart FET satisfies (e.g., is greater than or equal to) this storedthreshold.

The on-state connectivity test may be utilized independent of or inconjunction with the off-state connectivity described above. Theon-state connectivity is particularly difficult for use with LEDs as thelow amount of current that illuminates LEDs. The on-state connectivityconducts its assessment as the lights are being turned on so that it canilluminate the lights to conduct the aforementioned assessment. Theon-state connectivity doesn't need to prevent illumination of the lightsas does the off-state connectivity assessment. Further, a firstoff-state connectivity assessment (such as the described above) may beconducted. If there is a failure or an inconclusive result, a firston-state assessment may be conducted. This pattern may be repeated orany combination of off-state and on-state connectivity assessments maybe performed.

The system described herein facilitates conducting the off-stateconnectivity test without illuminating the lamps/lights of the towedvehicle. Additionally, having the lamps/lights illuminate during theoff-state connectivity test may render the test ineffective. Also, thesystem described herein does not turn on the lamp/lights inadvertentlywhen not intended those lamps/lights are not being used for theirintended purpose. Further, while the system disclosed herein isdisclosed as applying to a towed vehicle, the system could also beapplied to a towing vehicle such that the system could detect the statusof the lights/lamps of the towing vehicle as described above. Further,the system disclosed herein may be utilized to determine a status (e.g.,connected or disconnected) of the electrical connection between thetowing vehicle and towed vehicle as well as the status of thelights/lamps of the towed vehicle and/or even the towing vehicle. Thisstatus information may be utilized in operation of other towingaccessories or components. For example, the information regarding thestatus of the connection between the towing vehicle and towed vehiclemay be sent to another component of the towing system (such as a brakecontroller) or another processor/computing device (such as a smartphone,tablet, cloud computing system or the like). This status indicator maythen be used as part of a decision-making process, part of larger statusindicator (e.g., ready to tow or not ready to tow) or to cause anaction. An example of how this could be utilized is disclosed in U.S.Pat. No. 9,738,125, which is incorporated herein by reference.

Although the embodiments of the present invention have been illustratedin the accompanying drawings and described in the foregoing detaileddescription, it is to be understood that the present disclosure is notto be limited to just the embodiments disclosed, but that the disclosuredescribed herein is capable of numerous rearrangements, modificationsand substitutions without departing from the scope of the claimshereafter. The claims as follows are intended to include allmodifications and alterations insofar as they come within the scope ofthe claims or the equivalent thereof.

Having thus described the invention, the following is claimed:
 1. Asystem to determine a connection state of lamps of a trailer, the systemcomprising: connectivity circuitry electrically coupled to a connectorto provide a test signal to the lamps of the trailer and condition aresponse signal indicative of the connection state and the load profile;and processing circuitry electronically coupled to the connectivitycircuitry to determine the connection state and the load profile of thelamps of the trailer based on the response signal when the lamps of thetrailer are off, wherein the processing circuitry is configured to:detect when the lamps are powered on; and in response to detecting thatthe lamps are powered on, suspend generating the test signal while thelamps are powered on.
 2. The system of claim 1, wherein the processingcircuitry is configured to distinguish between at least three loadprofiles.
 3. The system of claim 2, wherein the processing circuitry isconfigured to distinguish between a first load profile indicative thatno lamps of the trailer are connected to the connector, a second loadprofile indicative that the lamps of the trailer are incandescent-basedlamps, and a third load profile indicative that the lamps of the trailerare light emitting diode-based lamps.
 4. The system of claim 3, whereinprocessing circuitry is configured to distinguish between the first loadprofile, the second load profile, and the third load profile based on atiming characteristic of the response signal.
 5. The system of claim 4,wherein processing circuitry is configured to determine that loadprofile of the lamps of the trailer is the first load profile based onthe timing characteristic being below a first threshold.
 6. The systemof claim 4, wherein processing circuitry is configured to determine thatload profile of the lamps of the trailer is the second load profilebased on the timing characteristic being between a first threshold and asecond threshold greater than the first threshold.
 7. The system ofclaim 4, wherein processing circuitry is configured to determine thatload profile of the lamps of the trailer is the third load profile basedon the timing characteristic being above a second threshold that isgreater than the first threshold.
 8. The system of claim 1, wherein theprocessing circuitry is configured to communicatively coupled to anelectronic control unit of a towing vehicle.
 9. The system of claim 1,further including lamp control circuitry separate from the connectivitycircuitry to control the on/off state of the lamps of the trailer, thelamp control circuitry communicably coupled to an electronic controlunit of a towing vehicle.
 10. The system of claim 1, wherein theprocessing circuitry defines a state machine to asynchronously controlthe connectivity circuitry to provide the test signal and determine theconnection state and load profile of the lamps of the trailer.
 11. Thesystem of claim 1, wherein the connectivity circuitry includes a rightlamp connectivity circuit and a left lamp connectivity circuit, andwherein the processing circuitry defines a test cycle to periodicallytest the connection state and the load profile of the lamps of thetrailer by causing the right lamp connectivity circuit to produce afirst test signal at a first time that generates a first response signaland causing the left lamp connectivity circuit to produce a second testsignal at a second time that generates a second response signal.
 12. Thesystem of claim 1, wherein test signal is a first test signal andwherein the connectivity circuitry is configured to provide a secondtests signal to the same one of the lamps as the first test signal. 13.The system of claim 12, wherein the processing circuitry is configuredto measure a first voltage at first current threshold of a signalgenerated in response to the first test signal and a second voltage at asecond current threshold of a signal generated in response to the firsttest signal, the first current threshold being different than the secondcurrent threshold.
 14. The system of claim 13, wherein the processingcircuitry is configured to detect a presence of corrosion between theconnector and the lamps based on a different between the first voltageand the second voltage.
 15. The system of claim 1, wherein a duration ofthe test signal is configured such that the lamps, when present, do notvisibly illuminate in response to the test signal.
 16. The system ofclaim 1, wherein the lamps are turn signal lamps of the trailer.
 17. Thesystem of claim 1, wherein the lamps are at least one of running lamps,fog lamps, reverse lamps, auxiliary lamps, or park lamps.
 18. A methodof determining a connection state of lamps of a trailer, the methodcomprising: monitoring an on/off state of the lamps of the trailer; andwhen the lamps of the trailer are off: generating a first ramp signalfor a first one of the lamps; monitoring a first response signalgenerated in response to the first ramp signal; generating a second rampsignal for a second one of the lamps; monitoring a second responsesignal generated in response to the second ramp signal; and categorizingthe connection state and a load profile of the lamps of the trailerbased on the first and second response signals.
 19. The method of claim18, wherein categorizing the connection state of the lamps of thetrailer based on the first and second response signals comprisesdistinguishing between at least three load profiles.
 20. The method ofclaim 18, wherein categorizing the load profile of the lamps of thetrailer based on the first and second response signals comprisesdistinguishing between a first load profile indicative that no lamps ofthe trailer are connected to the connector; a second load profileindicative that the lamps of the trailer are incandescent-based lamps;and a third load profile indicative that the lamps of the trailer arelight emitting diode-based lamps.
 21. The method of claim 20, whereindistinguishing between the first load profile, the second load profile,and the third load profile comprises distinguishing between the firstload profile, the second load profile, and the third load profile basedon a timing characteristic of the response signals.
 22. The method ofclaim 21, wherein distinguishing between the first load profile, thesecond load profile, and the third load profile comprises determiningthat the load profile of each of the lamps of the trailer is the firstload profile based on the timing characteristics being below a firstthreshold.
 23. The method of claim 21, wherein distinguishing betweenthe first load profile, the second load profile, and the third loadprofile comprises determining that the load profile of each of the lampsof the trailer is the second load profile based on the timingcharacteristic being between a first threshold and a second thresholdgreater than the first threshold.
 24. The method of claim 21, whereindistinguishing between the first load profile, the second load profile,and the third load profile comprises determining that the load profileof each of the lamps of the trailer is the third load profile based onthe timing characteristic being above a second threshold that is greaterthan the first threshold.
 25. A trailer light controller comprising: aleft lamp connectivity circuit electrically coupled to a connector toconnect to a left lamp of a trailer, the left lamp connectivity circuitto produce a first test signal and condition a first response signal,the first response signal having a first timing characteristic based ona connection status and a load profile of the left lamp; a right lampconnectivity circuit electrically coupled to the connector to connect toa right lamp of a trailer, the right lamp connectivity circuit toproduce a second test signal and condition a second response signal, thesecond response signal having a second timing characteristic based on aconnection status and a load profile of the right lamp; a left lampcontrol circuit coupled to the connector to connect to the left lamp tocontrol the on/off state of the left lamp; a right lamp control circuitcoupled to the connector to connect to right lamp to control the on/offstate of the right lamp; and processing circuitry configured to:categorize the connection state and the load profile of the left lampbased on the first timing characteristic of the first response signal,and categorize the connection state and the load profile of the rightlamp based on the second timing characteristic of the second responsesignal.
 26. The trailer light controller of claim 25, wherein theprocessing circuitry is configured to, for each of the left and rightlamps, distinguish between a first load profile indicative that thecorresponding lamp is not connected to the connector, and a second loadprofile indicative that the corresponding lamp is one of anincandescent-based lamp or a light emitting diode-based lamp.
 27. Amethod of determining a connection state of a lamp of a trailer, themethod comprising: monitoring an on/off state of the lamp of thetrailer; and when the lamp of the trailer is off: generating a rampsignal for the lamp; monitoring a response signal generated in responseto the ramp signal; categorizing the connection state and a load profileof the lamps of the trailer based on the response signal.
 28. A systemto determine a connection state of lamps of a trailer, the systemcomprising: connectivity circuitry electrically coupled to a connectorto provide a test signal to the lamps of the trailer and condition aresponse signal indicative of the connection state and the load profile;and processing circuitry electronically coupled to the connectivitycircuitry to determine the connection state and the load profile of thelamps of the trailer based on the response signal when the lamps of thetrailer are off wherein the processing circuitry is configured todistinguish between a first load profile indicative that no lamps of thetrailer are connected to the connector, a second load profile indicativethat the lamps of the trailer are incandescent-based lamps, and a thirdload profile indicative that the lamps of the trailer are light emittingdiode-based lamps based on a timing characteristic of the responsesignal.
 29. A system to determine a connection state of lamps of atrailer, the system comprising: connectivity circuitry electricallycoupled to a connector to provide a test signal to the lamps of thetrailer and condition a response signal indicative of the connectionstate and the load profile; and processing circuitry electronicallycoupled to the connectivity circuitry to determine the connection stateand the load profile of the lamps of the trailer based on the responsesignal when the lamps of the trailer are off wherein the processingcircuitry defines a state machine to asynchronously control theconnectivity circuitry to provide the test signal and determine theconnection state and load profile of the lamps of the trailer.
 30. Asystem to determine a connection state of lamps of a trailer, the systemcomprising: connectivity circuitry electrically coupled to a connectorto provide a test signal to the lamps of the trailer and condition aresponse signal indicative of the connection state and the load profile;and processing circuitry electronically coupled to the connectivitycircuitry to determine the connection state and the load profile of thelamps of the trailer based on the response signal when the lamps of thetrailer are off wherein the connectivity circuitry includes a right lampconnectivity circuit and a left lamp connectivity circuit, and whereinthe processing circuitry defines a test cycle to periodically test theconnection state and the load profile of the lamps of the trailer bycausing the right lamp connectivity circuit to produce a first testsignal at a first time that generates a first response signal andcausing the left lamp connectivity circuit to produce a second testsignal at a second time that generates a second response signal.
 31. Asystem to determine a connection state of lamps of a trailer, the systemcomprising: connectivity circuitry electrically coupled to a connectorto provide a test signal to the lamps of the trailer and condition aresponse signal indicative of the connection state and the load profile;and processing circuitry electronically coupled to the connectivitycircuitry to determine the connection state and the load profile of thelamps of the trailer based on the response signal when the lamps of thetrailer are off wherein test signal is a first test signal and whereinthe connectivity circuitry is configured to provide a second testssignal to the same one of the lamps as the first test signal.